This invention relates to an improved fire ladder and also to a method of constructing such a ladder.
Fire ladders of flexible construction have been developed in order to provide for the escape of persons from the upper stories of buildings during fires. Typically, these ladders include a pair of chains between which the rungs extend. Hooks or similar members are provided on the upper ends of the chains for attachment to a window sill or the like in order to suspend the ladder therefrom.
The flexible nature of the ladder permits it to be collapsed and stored in a box or the like. In the event of a fire, the hooks are attached to the window sill and the chains are thrown out of the window so that escape may be made down the ladder.
A serious problem with existing ladders of this type is the tendency of the chains to become twisted and tangled with one another and/or with the rungs when thrown out the window. Manifestly, such difficulties seriously compound the dangers in what is already an emergency situation. Chains are also relatively expensive and are susceptible to breaking and other damages and they take up a considerable amount of space so that storage of the ladder requires a large container. Connecting the rungs to the chains in a suitable manner also presents a problem in that the connections must be secure in order to avoid unsafe conditions, while they must at the same time be relatively simple and economical for practical reasons. In existing ladders, welding and other conventional types of connections are used.
The manner in which existing ladders are suspended from a building support such as a window sill has been generally unsatisfactory in that stability is lacking and the ladder sometimes is able to work itself free of the sill. It is desirable for the hook arms used to suspend the ladder to be connected to one another so that their spacing does not change to an excessive extent during use. Likewise, it is desirable for the arms to be foldable against one another for convenient storage. The flexible ladders that have been proposed have not been capable of convenient folding while at the same time adequately resisting collapse during use. Further, the scissors-like hinges that have been used to connect the hook arms present a serious safety hazard since they collapse when significant weight is placed on them, as when a foot is inadvertently placed on the hinge.
The present invention provides an improved ladder which is characterized by strong, flexible wire cables forming the opposite ladder sides. The cables are bent into loops and the loops are inserted into open ends of tubes that serve as the ladder rungs. The ends of each tube are forcibly collapsed such that one tube wall is flattened against the other in a manner to firmly clamp the cables within the ends of the tubes. This manner of construction provides a ladder which is not susceptible to becoming tangled since no chain links or other like structures are presented. Further, the rungs are mounted by means of a simple method which may be carried out with convention equipment and which results in secure connections between the rungs and cables. The upper surface of each rung is flattened and scored to conveniently receive the feet, while a unique hinge mechanism is provided to bias the support arms toward a spread position while permitting them to be conveniently folded to a collapsed storage position.
It is an important object of this invention to provide a ladder having flexible metal cables as opposite sides. The wire "rope" structure of the cables provides them with more than adequate strength, while avoiding the problems associated with chains such as the tendency of chain links to tangle with one another and with the rungs and to catch on snags and the like.
Another object of the invention is to provide a ladder of the character described wherein the rungs are secured to the cables in a unique fashion which enhances the overall strength of the ladder.
A further object of the invention is to provide a ladder of the character described which is simple and economical to construct and yet improved as to its safety and strength characteristics in comparison to existing ladders.
Yet another object of the invention is to provide a ladder of the character described wherein the rungs are constructed in a manner to readily accomodate the feet without slippage.
Still another object of the invention is to provide a ladder of the character described having support arms which are coupled together by a unique hinge arrangement that firmly maintains the arms in a spread apart position during use, while permitting the arms to be quickly and easily folded to a collapsed position for convenient storage.
An additional object of the invention is to provide a unique method of constructing a fire ladder which may be carried out quickly, easily and economically.
A still further object of the invention is to provide a method of the character described which results in secure connections of the ladder rungs to the metal cables which form the sides of the ladder. In addition, the necessity of welding the rungs is eliminated, as are the problems associated with welding and other conventional fastening means.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.